function [k] = FCkeff(k0, l, l_delta)
% Calculate the effective spring constant by accounting for tip angle 
% and off-end loading
%
% INPUT:    k0, spring constant obtained from Sader applet, N/m
%               Go to http://www.ampc.ms.unimelb.edu.au/afm/webapp.html to
%               find k0.
%           l, full length of cantilever, m
%           l_delta, distance from end of cantilever to point of loading, m

k = (k0/(cos(15*pi/180))^2)*(l/(l-l_delta))^3;  